JP2001160114A - Two-dimensional dot code and its reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make accurately readable a two-dimensional dot code. SOLUTION: Timing marks 32L and 32R are printed on the left and right sides of the data marks 33 of a two-dimensional dot code in every row. The existence/absence of the data mark 33 is judged with the position on a straight line obtained by connecting the centers of the marks 32L and 32R at its left and right edges as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional dot code and an apparatus for reading the same, and more particularly to a two-dimensional dot code and an apparatus for reading the two-dimensional dot code so that the dot code can be read more accurately.

[0002]

2. Description of the Related Art Recently, two-dimensional dot codes have been used in various fields. In the two-dimensional dot code, a plurality of cells as basic units are two-dimensionally arranged to represent a predetermined code.

A conventional two-dimensional dot code is
For example, in many cases, an image is taken by a video camera or the like, and the code is read from the image. However, in the two-dimensional dot code that is captured by the video camera and the code is determined from the image, it is necessary to increase the size of the cell as a basic unit to some extent. As a result, 2
There has been a problem that the dimensional dot code itself requires a relatively large area.

Therefore, a dot code has been proposed in which, when printing with a printer, a code is represented using a dot as its minimum unit as a basic unit.

That is, according to this dot code, for example, as shown in FIG. 1, the code is represented by the presence or absence of a dot as the smallest unit that can be expressed by the printer.
Therefore, more codes can be expressed in a narrow range.

[0006]

However, in such a two-dimensional dot code, the position of the dot changes due to variations in the head of the printer. As a result, for example, as shown in FIG. 1, dots may be printed at a print position P2 that is separated from the original print position P1 by a predetermined offset amount. In such a case, when the two-dimensional dot code is optically read by a scanner, if the offset is large, it is erroneously read that the dot is not printed even though the dot is actually printed. There was a fear that it would be done.

A printer for printing a two-dimensional dot code,
Alternatively, it is possible to prevent such reading errors to some extent by increasing the accuracy of the scanner that reads them, but for that purpose, it is necessary to manufacture printers and scanners with high accuracy, which increases costs. There was a problem. The present invention has been made in view of such circumstances, and it is an object of the present invention to accurately read a two-dimensional dot code without increasing the accuracy of a printing device or a reading device.

[0008]

A two-dimensional dot code according to the present invention has a dot having the same shape as a dot representing a code at both ends or one end of a dot representing the code on a straight line in a direction perpendicular to the direction in which the dots are read. , A timing mark indicating a position of a dot representing a code.

In the two-dimensional dot code, the position of the dot representing the code having the same shape as the dot representing the code is provided at both ends or one end of the dot representing the code on a straight line perpendicular to the direction in which the dots are read. Is provided. Accordingly, when transport unevenness occurs during reading, the timing mark expands in the same manner as the dot, so that the transport unevenness can be easily detected, and a two-dimensional dot code that can accurately read the dot is used. Can be provided. Further, the dot printing state can be estimated from the timing mark, and the code recognition rate can be increased.

The two-dimensional dot code is, for example, as shown in FIG.
Are two-dimensional dot codes. The code representing the code is, for example, the data mark 33 in FIG. The timing mark is, for example, the timing mark 32 of FIG.
L, 32R.

The size of the dot representing the code and the size of the timing mark can be the size of one dot in recording.

The timing mark can be formed by recording at the same position a plurality of times.

The dots may include dots for codes for error detection.

[0014] The reading device of the present invention comprises: first detecting means for detecting the position of a timing mark disposed at both ends or one end of a dot representing a code on a straight line perpendicular to the dot reading direction; The present invention is characterized by comprising a second detecting means for detecting a dot representing a code, which is disposed between the timing marks at both ends detected by the first detecting means and located between them.

[0015] In this reading apparatus, the code representing the code is arranged between the dots representing the code, with reference to the timing marks arranged at both ends or one end on a straight line in a direction perpendicular to the direction in which the dots are read. A dot is detected. This makes it possible to accurately detect the presence or absence of a dot.

The first detecting means comprises, for example, the dot code image processing circuit 66 of FIG. 7 for executing the processing of step S1 of FIG. 9, and the second detecting means comprises, for example, the step of FIG. It is composed of the dot code image processing circuit 66 of FIG. 7 that executes the processing of S6.

The second detecting means can search for a dot around the dot when there is no dot at the position based on the timing mark.

The dot includes a dot for an error detection code, performs error correction using the error detection code, and, when an error is detected, shifts from a position based on the timing mark. Error correction means for preferentially correcting an error caused by a dot having a large value can be provided.

The error correction means comprises, for example, a dot code image processing circuit 66 shown in FIG.

The second detecting means detects a displacement of the position of the dot arranged before the dot representing the code, and can detect the dot representing the code based on the displacement of the detected position. .

[0021]

FIG. 2 shows a configuration example of a printing apparatus to which the present invention is applied. The CPU 13 of the printing device 11
The print head transport device 15, the print head 16, and the paper transport device 17 are controlled in response to a command from the input unit 12 including buttons, switches, and the like. The print head transport device 15 transports the print head 16 in the sub-scanning direction in response to a command from the CPU 13. Print head 16
Prints the two-dimensional dot code 2 on the card 1 in response to the print head control signal from the CPU 13. The paper transport device 17 transports the card 1 to a predetermined position in response to a command from the CPU 13. The memory 18 stores data supplied via a network such as a LAN via the communication unit 14 under the control of the CPU 13.

The print head 16 includes a plurality of print nozzles 10.
1 and ejects ink 102 to the card 1 to print a two-dimensional dot code 2 composed of dots.

Next, the operation will be described. When the user instructs printing by operating the input unit 12, the CPU 13
Captures print data via the communication unit 14 and stores the print data in the memory 18. Then, the CPU 13 controls the paper transport device 1
7 to convey the card 1 to a predetermined position. Further, the CPU 13 converts the received print data into a print head control signal, and supplies the print data to the print head 16.
The print head transport device 15 is controlled to move the print head 16 relative to the card 1 in the sub-scanning direction. The plurality of print nozzles 101 of the print head 16 eject ink 102 from each, and prints a two-dimensional dot code 2 composed of dots on the card 1.

FIG. 3 shows an example of the configuration of the two-dimensional dot code 2 printed on the card 1 in this manner. In the example of FIG. 3, the start position mark 31 is printed at the beginning with one line of dots. Then, one blank line is left, and the left and right timing marks 32L and 32R are set.
And the data mark 33 are printed. The dots forming the left and right timing marks 32L and 32R are printed in all rows. The dots constituting the data mark 33 are printed corresponding to the code. In the case of this example, the sizes of the dots constituting the timing marks 32L and 32R and the data mark 33 are both
Is the size of one print nozzle 101.

Printing is performed in order from the start position mark 31 in FIG. 3 from top to bottom (sub-scanning direction). In other words, the print head 16 is transported from top to bottom.

As will be described in detail later, when the timing marks 32L and 32R are printed in this way, the presence or absence of a dot is determined on a straight line connecting the timing marks 32L and 32R at both left and right ends. By doing so, it is possible to accurately determine the presence or absence of the dots constituting the data mark 33.

When the diameter of one dot is large, as shown in FIG. 3, the timing marks 32L, 32R are provided for each row.
Is printed, the timing mark 32
The dots constituting L and 32R may overlap. In such a case, for example, as shown in FIG.
The timing marks 32L and 32R can be printed at predetermined intervals (every line in the example of FIG. 4). Alternatively, as shown in FIG. 5, the timing marks 32L and 32R are alternately displayed (when the timing mark 32L is printed, the timing mark 32R is not printed on the line, and when the timing mark 32R is printed, , The timing mark 3 in that line
2L is not printed).

By doing so, it is possible to prevent the timing marks 32L and 32R from overlapping in the vertical direction. As a result, the positions of the timing marks 32L and 32R can be accurately detected, and the presence or absence of the data mark 33 based on the positions can be accurately determined.

As described above, the timing marks 32L, 3
Since 2R is a reference for reading the data mark 33, it is necessary to print and read as reliably as possible. Thus, for example, as shown in FIG. 6, the data mark 33 is printed only once, but the timing marks 32L and 32R may be printed a plurality of times. In this way, as shown in FIG. 6, the dots 41 forming the timing marks 32L and 32R are expressed in a darker color than the dots 42 forming the data mark 33, and the reading is performed at the time of reading.
The color of the ink is light, and even if it is printed, there is less fear that it cannot be read.

FIG. 7 shows an example of the configuration of a reading device for reading the card 1 on which the two-dimensional dot code 2 is printed as described above. The reading device 61 has a control circuit 62 composed of, for example, a microcomputer and the like.
Is controlled to generate light for illuminating the card 1 on which the two-dimensional dot code 2 is printed. The reading element 64 constituted by a CCD line sensor or the like is controlled by the control circuit 62 to read the two-dimensional dot code 2 of the card 1 and output the read image signal to the A / D converter 65. The A / D conversion unit 65 performs A / D conversion on the input image signal and outputs the signal to the dot code image processing circuit 66. A synchronization signal synchronized with the reading of the two-dimensional dot code 2 is supplied from the control circuit 62 to the dot code image processing circuit 66. The dot code image processing circuit 66 reads the image data input from the A / D converter 65 in synchronization with the synchronization signal, and outputs the read result to an external device.

At the time of reading, when the reading element 64 is electronically scanned in the main scanning direction (horizontal direction in FIG. 3), it is scanned in the sub-scanning direction (top to bottom in FIG. 3).

The resolution of the reading device 61 is higher than the resolution of the printing device 11. For example, if one dot printed by the printing device 11 corresponds to 3 × 3 pixels of the reading device 61,
The image read by the reading device 61 is as shown in FIG. That is, of the 3 × 3 pixels, the central 1
The pixel has the highest density, the four upper, lower, left and right pixels subsequently have the higher density, and the density of the four pixels obliquely adjacent to each other is the lowest.

Next, referring to the flowchart of FIG.
The dot reading process will be described. First, in step S1, the dot code image processing circuit 66 executes a process of detecting the start position mark 31. Step S
In 2, the dot code image processing circuit 66 determines whether or not the start position mark 31 has been detected. If the start position mark 31 has not been detected, the process returns to step S1, and the detection processing of the start position mark 31 is executed again. Start position mark 31
As shown in FIG. 3, is printed in a row in a direction perpendicular to the transport direction (sub-transfer operation direction) of the card 1 over a predetermined width, so that the detection can be confirmed. it can.

When the start position mark 31 is detected, the process proceeds to step S3, where the dot code image processing circuit 66
The center coordinates of the start position mark 31 are calculated. For this detection, the details will be described later, but a dot detection process shown in FIG. 13 may be executed.

Next, proceeding to step S4, the dot code image processing circuit 66 determines whether the timing marks 32L, 32R
Is performed. Then, in step S5, the dot code image processing circuit 66 determines whether or not the timing marks 32L, 32R have been detected. If not detected, the process returns to step S4 and executes the detection process again. As shown in FIG. 3, the timing marks are printed on the left and right ends of the data mark 33 in a direction perpendicular to the start position mark 31 (a direction parallel to the sub-scanning direction). can do. In this detection, the dot detection process shown in the flowchart of FIG. 13 may be executed.

If the timing marks 32L and 32R have been detected, the process proceeds to step S6, where the dot code image processing circuit 66 executes a one-line dot detection process. The details thereof will be described later with reference to the flowcharts of FIGS. 10 and 11. Here, the presence or absence of one line of dots of the data mark 33 is determined. Then, in step S7, the dot code image processing circuit 66 determines whether or not the processing of the data marks 33 corresponding to the timing marks 32L and 32R of all rows has been completed. Returning to step S4, the subsequent processing is repeated.
In step S7, the timing marks 3 for all rows
If it is determined that the reading process of the data mark 33 corresponding to 2L, 32R has been completed, the process is terminated.

Next, the details of the one-row dot detection processing in step S6 in FIG. 9 will be described with reference to the flowcharts in FIGS. First, in step S21, the dot code image processing circuit 66 detects the coordinates of the timing marks 32L and 32R at both ends. For example, assuming that the processing of the third row from the top in FIG. 12 is being performed, the x-coordinate and the y-coordinate of the timing marks 32L1 and 32R1 are detected. That is, the coordinates of points P1 and P12 in FIG. 12 are detected. Next, step S
At 22, the dot code image processing circuit 66 resets the counter that counts the number of columns in this case.

In step S23, the dot code image processing circuit 66 calculates a straight line L1 obtained by connecting the centers of the timing mark 32L1 and the timing mark 32R1, and further defines the start position mark 31 on the straight line L1. Coordinates x2, y2 (ideally, the value of y2 is equal to the value y1 of the y coordinate of the point P1) that defines the leftmost dot position of the data mark 33 to be written.
Is calculated. That is, the coordinates (x2,
y2) is calculated. Next, in step S24, the dot code image processing circuit 66 increments the value of the counter reset in step S22 by 1, and in step S25, determines whether or not the value of the counter has become larger than the number of columns of the data mark 33. , That is, data mark 3
It is determined whether or not the processing has been completed for all the columns of No. 3; if not, the process returns to step S23 to execute processing for calculating the reference coordinates of the next column.

As described above, when it is determined in step S25 that the reference coordinates of all the columns have been obtained, the process proceeds to step S26, where the dot code image processing circuit 66 clears the value of the counter. Next, step S
At 27, the dot code image processing circuit 66 executes a dot detection process. For details of this dot detection process,
This is shown in the flowchart of FIG. The processing of the flowchart in FIG. 13 is performed for the following purpose. That is, for example, as shown in FIG.
If No. 1 is printed out of the original print position (reference coordinates) P21, it may be determined that dots are not printed at the print position P21. Therefore, in the present invention, as shown in FIG.
Then, the center coordinates are moved within the search range W, and it is determined whether or not a dot exists within the search range W.

First, in step S61 of FIG.
The dot code image processing circuit 66 determines whether or not the density of the pixel at the coordinate (x, y) of interest is greater than a predetermined threshold. For example, it is determined whether or not the density of the pixel at the point P2 shown in FIG. 12 is higher than a predetermined threshold. If the density of the pixel is larger than the threshold, the process proceeds to step S62, and the dot code image processing circuit 66 determines that there is a dot at the reference position.

If it is determined in step S61 that the density of the pixel at the coordinates (x, y) of interest is equal to or smaller than a predetermined threshold value, the flow advances to step S63. The dot code image processing circuit 66 resets a built-in counter. In this case, this counter indicates the number of times of searching within the search range W described with reference to FIG.

Next, in step S64, the dot code image processing circuit 66 sets the coordinates (x,
The density of eight pixels around the pixel of y) is checked. That is,
Since the pixel at the coordinates (x, y) of interest is the central pixel of 3 × 3 pixels, the four pixels at the top, bottom, left and right,
In addition, the densities of four pixels obliquely adjacent to each other are checked.

Next, in step S65, the dot code image processing circuit 66 moves the pixel at the center of the dot to the pixel having the highest density (x ', y') among the eight pixels. In the case where there are a plurality of pixels having the highest density among the surrounding eight pixels, as shown in FIG. 16, the order of movement from the upper left to the lower right is set in advance, The movement is performed to the pixel having the higher priority. Then, in step S66, it is determined whether or not the density of the pixel at the coordinates (x ′, y ′) after the movement is greater than the threshold. This threshold is a threshold having the same size as the threshold in step S61. If it is determined in step S66 that the density of the pixel at the coordinates (x ', y') of interest is greater than the threshold, the process proceeds to step S62, where the dot code image processing circuit 66 prints a dot at that position. It is determined that it has been performed.

In step S66, it is determined whether the density of the pixel at the coordinates (x ', y') of interest is equal to the threshold.
If it is determined that the value is smaller than that, the process proceeds to step S67, where the dot code image processing circuit 66 increments the value of the counter indicating the number of times of movement to the surrounding eight pixels by one. The coordinates (x ′, y ′) that exist are the coordinates (x, y) of the center of 3 × 3 pixels.
y). That is, the pixel at the center of the 3 × 3 pixels is moved by this.

Next, in step S69, the dot code image processing circuit 66 determines whether or not the value of the counter is smaller than a predetermined number of times (for example, two times) set in advance. Returning to step S64, the subsequent processing is repeatedly executed.

If it is determined in step S69 that the value of the counter is not smaller than the specified number (if it is determined that the value is equal to the specified number), the process proceeds to step S70, where the dot code image processing circuit 66 sets , It is determined that there is no dot.

Returning to FIG. 11, after the dot detection process is performed in step S27 as described above, the process proceeds to step S28, where the dot code image processing circuit 66
Determines whether a dot has been detected. If it is determined that a dot has been detected, the process proceeds to step S29, where the dot code image processing circuit 66 detects the reference coordinates (x, y) that are currently targeted and the dot coordinates detected in the dot detection process in step S27. Dot center coordinates (x ', y')
Is calculated. This distance d is expressed by the following equation.

D = ((xx ′) ² + (yy ′) ² ) ^1/2 Next, in step S30, the dot code image processing circuit 66 calculates the coordinates of the dots detected in step S27. Check with the detection dot list. That is, as shown in FIG. 17, the dot code image processing circuit 66 stores the detected dot list in the built-in memory in step S36 described later.
In, the coordinates (detected X coordinate and detected Y coordinate) of the dot calculated in step S29 are registered together with the distance d of the coordinate from the reference coordinate and the reference position number corresponding to the detected dot. For each registration, Figure 17
As shown in FIG. Here, the reference position number is, for example, as shown in FIG. 12, from the leftmost coordinate x2 of the data mark 33 to the rightmost coordinate x2.
These numbers are assigned to the respective reference positions up to 11. In the example of FIG. 12, numbers 1 to 10 are set as reference position numbers.

In step S31, the dot code image processing circuit 66 determines whether or not the coordinates corresponding to the coordinates just detected are registered in the detected dot list. If the corresponding coordinates are not registered, FIG.
As shown in step S36, the center coordinates (x ', y') of the detected dot, the reference position number corresponding to the reference coordinates at that time, and the distance d calculated in step S29 are stored in the detected dot list. be registered. further,
In step S37, the dot code image processing circuit 6
6 sets the value of the dot detection result of the reference position number to be processed in the dot detection result list of the built-in memory to 1, as shown in FIG.

If it is determined in step S31 that the coordinates corresponding to the coordinates of the detected dot have already been registered in the detected dot list, the process advances to step S32, where the dot code image processing circuit 66 Distance d 'corresponding to the coordinates already registered in the list
(Read). Then, in step S33, the dot code image processing circuit 66 performs step S33.
The distance d calculated in step 29 is compared with the distance d ′ read from the detection dot list, and the distance d is larger than the distance d ′.
If it is smaller, the process proceeds to step S34, and the value as the dot detection result of the reference position number corresponding to the coordinates of the detected dot in the detected dot list is corrected to 0.
As shown in FIG. 18, the dot detection result list stores reference position numbers, their reference coordinates (reference X coordinate, reference Y coordinate), and dot detection results. A value of 1 in the dot detection result indicates that the dot of the reference position number has been detected, and a value of 0 indicates that the dot corresponding to the reference position number has not been detected.

In step S35, the dot code image processing circuit 66 uses the detected dot list (FIG. 17)
The data of the detected coordinates that have already been registered are deleted because of the erroneous determination.

Further, in step S36, the dot code image processing circuit 66 calculates the coordinates of the dot detected in step S27, the reference position number currently being processed, and the distance d calculated in step S29. Register in the detection dot list (FIG. 17). Further, in step S37, the dot code image processing circuit 66
In the dot detection result list (FIG. 18), the value of the dot detection result of the reference position number to be processed is set to 1.

On the other hand, if it is determined in step S33 that the distance d is not smaller than the distance d ', the process proceeds to step S33.
Proceeding to 39, the dot code image processing circuit 66 sets the dot detection result of the reference position number to be processed to 0.
Set to.

In this way, as shown in FIG. 19, the dot to be printed at the original position (reference coordinates) A is
Is determined, the dot at position C is determined to be printed at position A, and then the dot at position C is determined to be printed at the next position (reference coordinates) B as well. That is, it is prevented that the dot at position C is double-determined as being printed at both position A and position B.

After steps S37, S38 and S39, the process proceeds to step S40, where the dot code image processing circuit 66 increments the value of the counter by one. In step S41, the dot code image processing circuit 66
Is to determine whether the value of the counter incremented in step S40 is larger than the maximum value of the number of dots of the data mark 33 included in one row (the number of columns of the data mark 33), and Returns to step S27, and the subsequent processing is repeatedly executed.
If it is determined in step S41 that the value of the counter has become larger than the maximum value of the number of dots in one line, the process ends.

In some cases, dots may be printed out of alignment depending on the shape of the print nozzle 101. Even in such a case, the dots can be read accurately.

In the case of this example, the timing marks 32L,
As shown in FIG. 20, for example, as shown in FIG. 20, the dots of 32R and the data mark 33 have the same shape (both are formed by one nozzle).
The timing marks 32L2 and 32R2 are similarly shifted (moved upward) from the data marks 33 located on the straight line L2 connecting the centers thereof, so that the dots can be read accurately by the above-described dot reading processing.

The reading device 61 is constituted by a manual operation type, and the reading device 61 is manually operated by the user on the card 1 so that the two-dimensional dot code 2 printed on the card 1 is read. In this case, the relative transfer speed between the card 1 and the reading element 64 may not always be the reference transfer speed. For example, if the relative transfer speed is lower than the reference transfer speed, one dot originally read by 3 × 3 pixels is shown in FIGS. 21 and 22 when the relative speed is の of the reference speed. Thus, reading is performed with 16 pixels. That is, at this time, the number of pixels in the main scanning direction (horizontal direction in FIGS. 21 and 22) does not change, but the number of pixels in the sub-scanning direction (vertical direction in FIGS. 21 and 22) is Six, four on the left and right. In such a case, the image expands in the sub-scanning direction but does not expand in the main scanning direction. Therefore, as shown in FIGS. 21 and 22, the search range W is set in the sub-scanning direction (relative to the card 1). (In the transport direction). Accordingly, even when the relative transport speed of the card 1 in the sub-scanning direction changes and the image expands in the sub-scanning direction, it is possible to more reliably detect the dots.

FIG. 22 shows a case where the relative speed is reduced to half of the reference speed when reading one line of dots.

For example, as shown in FIG. 21, when the timing mark expands and contracts in the card transfer direction, to correct this, the timing mark detection processing in step S4 of FIG. 9 is performed as shown in the flowchart of FIG. Done in That is, in step S91, the dot code image processing circuit 66 sets the left timing mark 32
L is detected, and in step S92, the aspect ratio of the left timing mark 32L is calculated. This aspect ratio is a value obtained by dividing the length of the detected dot in the vertical direction by the length of the dot in the horizontal direction, and is 2 (= 6/3) in the example of FIG.

Next, in step S93, the dot code image processing circuit 66 sets the right timing mark 32
R is detected, and in step S94, the aspect ratio of the right timing mark 32R is calculated. Step S9
In 5, the dot code image processing circuit 66 calculates the average of the aspect ratio calculated in step S92 and the aspect ratio calculated in step S94. Then, Step S96
In FIG. 21, the dot code image processing circuit 66 is obtained by multiplying the length of the original search range W1 in the vertical direction (Y direction) by the average aspect ratio calculated in step S95, as shown in FIG. Let the value be the length of the corrected search range W2 in the vertical direction.

Thus, when the length of the dot expands or contracts in the sub-scanning direction, the search range is changed according to the expansion or contraction ratio. As a result, more accurate determination processing of the presence or absence of a dot becomes possible.

In the above description, the timing mark 32L and the timing mark 32R are provided at the left and right ends as an example. However, the timing mark 32L and the timing mark 32R may be provided at only one of the ends.

FIG. 24 shows another example of the two-dimensional dot code. In this example, the start position mark 31 shown in FIG. 3 is printed on a plurality of lines (five lines in the example of FIG. 24), and is used as a printer head offset detection mark 51. The detection mark 51 is a dot 3 printed on the same row as the timing marks 32L and 32R.
2L-1 to 32L-5, 32R-1 to 32R-5,
And dots 31-1-i (i = 1, 2,..., 5) arranged in a row corresponding to each row of the data mark 33.
Through 31-ji (j represents the column of the data mark 33)
It consists of.

As described above, when the detection mark 51 is printed, the dot code image processing circuit 66 detects the start position mark in step S1 in FIG. Execute the detection process.

In step S101, the dot code image processing circuit 66 resets a built-in counter,
In step S102, the built-in buffer is cleared. In step S103, the dot code image processing circuit 66 sets the timing marks 32L and 32R at both ends.
The coordinates of are detected. In step S104, the dot code image processing circuit 66 sets the left and right timing marks 3
The reference coordinates of each dot obtained by dividing the straight line obtained by connecting the centers of 2L and 32R by the number of rows of the data mark 33 are calculated.

Next, in step S105, the dot code image processing circuit 66 executes the dot detection processing described with reference to the flowchart of FIG. And
In step S106, the dot code image processing circuit 66 calculates the offset amount of the currently detected dot from the reference coordinates. When the reference coordinates are (x, y) and the center coordinates of the detected dot are (x ′, y ′), the offset amount in the x direction is expressed by the following equation.

Dx (i, j) = x-x 'The offset amount in the y direction is represented by the following equation.

Dy (i, j) = y-y '

In the above equation, i represents a row number, and j represents a column number.

Next, in step S107, the dot code image processing circuit 66 stores the offset amount calculated in step S106 in a buffer. Step S10
In step 8, the dot code image processing circuit 66 determines whether or not the processing for the dots in each column for one row has been completed. Returning to S105, the subsequent processes are repeatedly executed.

If it is determined in step S108 that the process of detecting the offset amount for each dot of one line has been completed, the process proceeds to step S110, where the dot code image processing circuit 66 indicates the number of processed lines. Increment the value of the counter by one. In step S110, the dot code image processing circuit 66 determines whether or not the value of the counter has become larger than the specified number of lines set as the printer head offset detection mark 51. Then, the process returns to step S103, and the subsequent processes are repeatedly executed.

If it is determined in step S110 that the value of the counter has become larger than the prescribed number of lines, the process proceeds to step S111, where the dot code image processing circuit 66
Reset the counter value. In step S112, the dot code image processing circuit 66 calculates the average value of the offset amount for all the rows in one column. In the case of the example of FIG. 24, the average value of the offset amounts for five rows in one column is calculated.

The average value of the offset amount is schematically shown in FIGS. 26 and 27. That is, for example, as shown in FIG.
X coordinates of each of 1 to 31-2-5 are x
When 2-1 to x2-5, the average value xa of these x coordinates is calculated by the following equation.

Xa = (x2-1 + x2-2 + x2-3 +
x2-4 + x2-5) / 5

The average value xa thus obtained is
The coordinate x-2 is representative of the dot 31-2 in that row. This value is used as the coordinate x2 shown in FIG.

Further, as shown in FIG.
-1 and 32R-1 and a straight line connecting the dots 32L-5 and 32R-5 to L1 to L5, respectively.
, Each dot 31-2-1 to 31-2-5
, And the differences y1 to y5 of the y coordinates with the straight lines L1 to L5 are obtained, and their average value ya is obtained as shown in the following equation.

Ya = (y1 + y2 + y3 + y4 + y5) / 5

Next, in step S113, the dot code image processing circuit 66 stores the average value calculated in step S112 in the buffer as the offset amount of the nozzle in the corresponding row. In step S114, the dot code image processing circuit 66 increments the value of the counter indicating the number of processed rows by one, and proceeds to step S1.
At 15, it is determined whether or not the value of the counter has exceeded a predetermined number of columns (the number of columns of the data mark 33 in FIG. 24). If it is determined that the value of the counter is not larger than the specified number of columns, step S112
And the subsequent processing is repeatedly executed. If it is determined in step S115 that the value of the counter has become larger than the value of the specified number of columns, the offset detection processing ends.

As described above, when the offset amount is calculated, the dot detection processing for one line shown in FIGS.
This is performed as shown in FIGS. 28 and 29. FIG. 28 and FIG.
The processing of steps S131 to S152 shown in FIG. 9 is basically the same as the processing of steps S21 to S41 shown in FIGS. However,
It corresponds to step S23 and step S24 in FIG.
Between step S133 and step S135 in FIG.
Step S134 has been added. Step S
In 134, the dot code image processing circuit 66 adds the offset amount obtained in the processing of FIG. 25 as described above to the reference coordinates calculated in step S133. That is, the reference coordinates (x, y) existing in the column j are corrected as follows.

(X + Dx (j), y + Dy (j)) Here, Dx (j) and Dy (j) correspond to column j
Mean value of the offset value in the x direction and the offset value in the y direction of the column j, and are expressed by the following equation.

[0082]

(Equation 1)

As a result, even if there is a variation in the mounting position of the print nozzle 101 for printing each dot of the print head 16, it is possible to perform the reading process while compensating for the variation. As a result, it is possible to accurately read the dots without significantly improving the accuracy of the printing device 11 or the reading device 61.

As described above, the dot code image processing circuit 66 determines the code based on the presence or absence of the dots constituting the data mark 33 and outputs the result of the determination. Code can be included. In this case, the dot code image processing circuit 66
Executes a code detection process as shown in FIG.

That is, first, in step S171, the dot code image processing circuit 66 detects a code composed of dots. It is determined whether or not there is an error in the code detected in step S172 by using an error detection code included in the code. If an error exists, the process proceeds to step S173, where the dot code image processing circuit 66 executes a process of preferentially correcting an error from the code corresponding to the dot having the largest deviation from the reference position. Then, the process returns to step S171, and the subsequent processes are repeatedly executed.

If it is determined in step S172 that there is no error, the process advances to step S174, where the dot code image processing circuit 66 determines whether or not the detection processing of all the codes has been completed, and the detection has not been completed. If there is a code that has not been executed, the process returns to step S171, and the subsequent processing is repeatedly executed. Step S1
If it is determined in 74 that the detection processing of all the codes has been completed, the processing is terminated.

In this way, the error correction processing can be completed quickly.

[0088]

As described above, according to the present invention, it is possible to provide a two-dimensional dot code that can be read accurately, and to accurately detect the presence or absence of a dot.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a conventional two-dimensional dot code.

FIG. 2 is a block diagram illustrating a configuration example of a printing apparatus to which the present invention has been applied.

FIG. 3 is a diagram illustrating an example of a two-dimensional dot code to which the present invention is applied.

FIG. 4 is a diagram illustrating an example of a two-dimensional dot code to which the present invention is applied.

FIG. 5 is a diagram illustrating an example of a two-dimensional dot code to which the present invention is applied.

FIG. 6 is a diagram illustrating an example of a two-dimensional dot code to which the present invention is applied.

FIG. 7 is a block diagram illustrating a configuration example of a reading device to which the present invention has been applied.

8 is a diagram illustrating an example of an image read by the reading device of FIG. 7;

FIG. 9 is a flowchart illustrating an operation of reading dots by the reading device of FIG. 7;

FIG. 10 is a flowchart illustrating details of a one-row dot detection process in step S6 of FIG. 9;

FIG. 11 is a flowchart illustrating details of a one-row dot detection process in step S6 of FIG. 9;

FIG. 12 is a diagram illustrating the dot detection process in step S27 of FIG.

FIG. 13 is a flowchart illustrating details of a dot detection process in step S27 of FIG. 11;

FIG. 14 is a diagram for explaining misregistration of printing of dots.

FIG. 15 is a diagram illustrating a search range.

FIG. 16 is a diagram illustrating the priority order of pixel density determination.

FIG. 17 is a diagram illustrating an example of a detection dot list.

FIG. 18 is a diagram illustrating an example of a dot detection result list.

FIG. 19 is a diagram illustrating double counting of dots that have been misaligned.

FIG. 20 is another diagram illustrating the dot detection process in step S27 of FIG. 11;

FIG. 21 is a diagram for explaining image expansion.

FIG. 22 is another diagram illustrating expansion of an image.

FIG. 23 is a flowchart illustrating a timing mark detection process in consideration of image expansion.

FIG. 24 is a diagram illustrating an example of a printer head offset detection mark.

FIG. 25 is a flowchart illustrating offset detection processing using the printer head offset detection mark of FIG. 24;

FIG. 26 is a diagram for explaining calculation of an average value of x coordinates.

FIG. 27 is a diagram illustrating the calculation of the average value of the y coordinate.

FIG. 28 is a flowchart illustrating details of one-row dot detection processing in step S6 of FIG. 9;

FIG. 29 is a flowchart illustrating details of one-row dot detection processing in step S6 of FIG. 9;

FIG. 30 is a flowchart illustrating a code detection process of the reading device of FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 card 2 two-dimensional dot code 11 printing device 12 input unit 13 CPU 14 communication unit 15 print head transport device 16 print head 61 reading device 62 control circuit 63 light source 64 reading element 66 dot code image processing circuit

Continuation of the front page (72) Inventor Hideki Nakajo 801 Shiomiji-dori Horikawa Higashiiri Minamifudodoucho, Shimogyo-ku, Kyoto F-term in OMRON Corporation (reference) 5B035 AA11 BB08 5B072 AA02 CC37 DD02 DD12 DD15 DD23 EE03 HH11 LL11 LL19 MM02

Claims (8)

[Claims] 1. A two-dimensional dot code in which dots are arranged two-dimensionally to represent a predetermined code, wherein both ends of a dot representing the code on a straight line in a direction perpendicular to a direction in which the dots are read or A two-dimensional dot code comprising, at one end, a timing mark having the same shape as the dot representing the code and representing the position of the dot representing the code. 2. The two-dimensional dot code according to claim 1, wherein the size of the dot representing the code and the size of the timing mark are the size of one dot in recording. 3. The timing mark is located at the same position,
The two-dimensional dot code according to claim 1, wherein the two-dimensional dot code is formed by recording a plurality of times. 4. The two-dimensional dot code according to claim 1, wherein the dots include dots for an error detection code. 5. A reading device for reading a two-dimensional dot code in which dots are two-dimensionally arranged to represent a predetermined code, wherein a straight line in a direction perpendicular to the direction in which the dots are read out of the dots representing the code. First detection means for detecting the position of a timing mark arranged at both ends or one end on the upper side, and the timing marks at both ends detected by the first detection means are arranged as a reference, A second detecting means for detecting the dot representing the code. 6. The reading device according to claim 5, wherein when the dot does not exist at a position based on the timing mark, the second detection unit searches for the dot around the dot. . 7. The dot includes a dot for an error detection code, performs error correction using the error detection code, and, when an error is detected, uses the timing mark as a reference. 7. An apparatus according to claim 6, further comprising an error correcting unit for correcting an error caused by a dot having a large deviation from a position to be corrected by priority.
A reading device according to claim 1. 8. The second detecting means detects a displacement of a position of the dot arranged before the dot representing the code, and represents the code based on a displacement of the detected position. The reading device according to claim 5, wherein the dot is detected.